1. Field of the Invention
The present invention relates to a vehicle body vibration control device for a vehicle such as an automobile, and more particularly, to a vehicle body vibration control device configured to suppress vibration of a vehicle body, which is caused by fluctuation in driving force of the vehicle.
2. Description of the Related Art
Vehicles such as automobiles travel by a driving force generated by a driving unit such as an engine. Fluctuation in driving force generated from the driving unit causes loads to be applied on the vehicle body in a fore-and-aft direction and a vertical direction of the vehicle relative to wheels. Thus, pitching vibration occurs in the vehicle body. Therefore, it has been suggested that the pitching vibration of the vehicle body be reduced through appropriate control of a command driving force to the driving unit.
For example, Japanese Patent Application Laid-open No. 2007-8421 filed by the applicant of this application describes a vehicle body vibration control device configured based on the above-mentioned concept. This vehicle body vibration control device includes a request driving force calculation unit configured to calculate a driver's request driving force, a driving unit configured to apply a driving force to a vehicle, a driving force control unit configured to control the driving unit based on a command driving force, and a notch filter configured to receive a signal indicating the request driving force from the request driving force calculation unit. The notch filter has a notch frequency set to a value for reducing a frequency component of vibration of a vehicle body. The notch filter subjects the signal to filter processing, and outputs the processed signal to the driving force control unit as a signal indicating the command driving force.
When vehicle traveling control, which is any one of cruise control, brake assist control, and anticollision control, is involved in control of the driving force of the vehicle, damping control based on the command driving force generated through the notch filter processing is not executed. As a result, according to the vehicle body vibration control device of this type, the vehicle body vibration can be reduced by the damping control when the vehicle traveling control is not executed. When the vehicle traveling control is executed, the damping control can be prevented from adversely affecting the vehicle traveling control.
The command driving force in the vehicle such as an automobile is calculated by an electronic control unit such as a microcomputer, and the command driving force is calculated through the notch filter at every predetermined time based on a driver's past request driving force, a current request driving force, and a past command driving force. Accordingly, the driver's request driving force is smoothed through the filter processing, and the command driving force is generated. This causes reduction of responsiveness of increase or decrease of a driving force of a driving source to a change of the request driving force. In a state where the request driving force increases or decreases in stages, a delay of a change of the command driving force with respect to the change of the request driving force is inevitable.
An effect of the damping control based on the command driving force generated through the notch filter processing becomes higher as a notch degree of the filter becomes higher. However, the delay of the change of the command driving force with respect to the change of the request driving force becomes larger as the notch degree becomes higher. The delay of the change of the command driving force with respect to the change of the request driving force is large when the request driving force changes in stages, and becomes larger as a difference in change of the request driving force between stages becomes larger.
When the delay of the change of the command driving force with respect to the change of the request driving force is large, the driver may feel that responsiveness of the driving unit to a driving operation has been reduced, and thus feel uncomfortable.
In the above-mentioned driving force control unit described in Japanese Patent Application Laid-open No. 2007-8421, similarly, the damping control is performed when the vehicle traveling control is not executed. Thus, this driving force control unit cannot prevent the driver from feeling uncomfortable due to feeling that responsiveness of the driving unit has been reduced.